Solar Power

Why should you consider solar technology?

The hotel sector is energy-intensive. Using cleaner and cheaper energy sources will help to reduce operational costs and increase competitiveness and sustainability.

In the UK, the hospitality sector spends over £1bn every year on energy. It is responsible for producing 3.5m tonnes of carbon emissions per year, but if the hotel industry reduced its energy bill by 20%, it could save a combined £200m, according to the Carbon Trust, the UK’s leading authority on carbon reduction.

According to the US federal government’s Energy Star programme, US hotels spend an average of $2,196 per room each year on energy. Not only is that a significant expenditure, it requires the burning of huge amounts of fossil fuels.

An option for many businesses is to source their own energy and in most cases solar power is the only realistic alternative.

A study by Sage Blossom Consulting of 4,400 hotels in the US found 12% used some form of alternative energy. And that figure looks set to grow as hoteliers look for more environmentally friendly and cheaper energy sources, and more incentives are offered for the implementation of renewable energy, including solar technology.

One initiative is the European Union (EU) co-funded Hotel Energy Solutions scheme, coordinated with the UN World Tourism Organization, United Nations Environment Program, International Hotel & Restaurant Association, European Renewable Energy Council and the French Environment and Energy Management Agency. The scheme has been set up to help small- and medium-sized hotels in the EU to increase energy efficiency and use renewable technologies.

The United Nations climate change conference in Copenhagen in December could also be good news for renewable energy. If targets for reducing carbon emissions are agreed, governments may provide more financial help to businesses to install solar technology.

The St Regis Aspen Resort
The St Regis Aspen Resort is making major strides in decreasing its carbon footprint with completion of a solar project that could reduce the hotel’s natural gas usage seasonally by as much as 30%.

One of the first hotels in America to use e-tube solar technology, its solar contractor, Altech Solar, began installing solar e-tubes in December 2008. A year later, it has mounted over 1,300 tubes on the roof, which will utilise the sun as a natural heat source.

Using the sun’s energy, solar e-tubes—also known as heat pipes—are capable of heating water in the vacuum tube arrays to temperatures above 400°F. The heated water circulates through the top of the tubes, where it is pumped into storage tanks and dispersion loops.

This system is tied into the resort’s main domestic water loop where it provides heat for domestic sinks and showers, the resort’s Remède spa and the swimming pool and whirlpools.

A sophisticated digital system regulates pumps, valves and water quantity to maintain the desired water temperature. Solar-heated water supplements and takes the place of natural, gas-heated water until the temperatures in those tanks drop below a set minimum temperature, for example, after the sun goes down or dense cloud cover appears. At that point, the system seamlessly reverts to heating the building’s water with natural gas, until the cycle starts the next day.

"The St Regis Aspen and our parent company, Starwood Hotels & Resorts Worldwide, made a large capital investment in this project as part of our green initiatives," says St Regis Aspen Resort general manager Senih Geray. "We are committed to significantly reducing the energy used by the hotel, because we believe in working toward a more sustainable and ecologically sound future."

The sun’s rays (solar radiation) offer a huge potential source of energy that can be used to heat, cool and light buildings. It’s been estimated that more energy from the sun falls on our planet in one hour than is used by in the world in one year.

The three main solar technology systems that convert sunlight into energy are:

Solar water-heating
By far the most commonly used, this solar technology produces hot water. Solar panels collect the energy, which directly heats the water system.

Solar photovoltaics
This converts sunlight into electricity via cells. The technology was discovered by scientists in 1954 and it has been transferred to small devices such as solar calculators and watches.

Passive solar design
New buildings can be designed to collect, store, and distribute solar energy. Features could include south-facing windows and building materials (thermal mass) that absorb and slowly release the sun’s heat.

Saving the planet is all well and good but what return can you expect to make on your green investment?

No matter what solar technology you install, you will start saving on your energy bills immediately and, depending on the system and the prices charged by your local energy provider, you can expect to offset the start-up costs within four to 12 years. Most systems have a 25-year manufacturers’ guarantee and a working life of over 40 years.

Start-up costs alone may put many businesses off but most governments offer grants, interest-free loans and tax rebates to cut the cost dramatically. Businesses can often claim up to 80% of the start-up costs depending on the country.
Disruption to hotels when fitting solar systems is normally minimal, as most work is carried out on roof areas far away from guests and staff.

San Francisco’s Hotel Carlton put in a large photovoltaics system that cost $163,951 but after rebates and tax credits the net cost to them was only $13,727. It is currently producing around 12% of the property’s electricity and it will pay for itself within four years. The system is also stopping 32,648 pounds of carbon a year from entering the atmosphere.

A UK government study carried out by the Carbon Trust found cutting electricity bills by 20% increases profits equivalent to a 5% rise in occupancy. But the economics of solar technology depends on local factors, as hotel group Accor discovered. It has 4,000 hotels and 500,000 rooms in 90 countries. “Savings vary depending on sunshine levels,” says Accor spokeswoman Delphine Dumonceau. “We’ve found that the economic payback time varies. In France, it is between 10 and 15 years, but in Morocco the payback time is shorter, around seven years.”

David Matthews, chief executive of the UK-based Solar Trade Association, adds: “Solar thermal saves on the heating bills and photovoltaics saves on electricity bills. The savings are directly related to how much solar technology one can install, which depends on factors such as the roof size, and also how much of the heat load can be covered. It’s a case-by-case, budget-by-budget basis per building.”

Aloft Hotel
More than 90% of the hot water at Abu Dhabi National Exhibitions Company’s (ADNEC) new Aloft Hotel, operated by Starwood Hotels & Resorts Worldwide, is supplied through energy harnessed from solar panels.

Covering an area of 2,300 square metres, 560 solar panels have been installed on the roof of one of the ADNEC car parks. These panels heat water for the hotel's 408 bedrooms, two production kitchens, food and beverage outlets, hotel offices and the swimming pool, saving an estimated 870 mega watt hours of electricity every year by making use of the infra-red component of sunlight to generate energy. The solar panels were manufactured in Germany by Wolf, a renowned leader in the solar power sector.

Commenting on the project, His Excellency Ali Saeed Bin Harmal, managing director of ADNEC, said, "In line with the Abu Dhabi government's 2030 vision for sustainable economic development, we are following the environmental objectives of the emirate by diversifying our power requirements away from traditional sources of energy. As the world’s most modern exhibition centre, we have a responsibility to lead from the front and this initiative, combined with other power saving programmes underway at ADNEC, re-enforces our position as the Middle East’s leading venue."

New-build hotels are able to incorporate all three systems—solar water-heating, solar photovoltaics and passive solar design—to become as self-reliant on electricity as possible no matter where in the world they are located.

Existing hotels have the option of installing solar water heating, solar photovoltaics or both. Solar water-heating is by far the most popular and cheaper option and can produce great savings as well as cut CO² emissions. Hot water is a constant requirement for any hotel and this system can reduce the need for conventional water heating by as much as two-thirds.

Most of these systems have two main components—a solar collector made up of large solar panels, normally on the roof, and a modified water tank. Systems can be either active or passive. The former is most common and uses an electric pump to circulate the hot water while passive systems rely on gravity and natural thermal currents to circulate the water.

In a solar swimming pool heating system, the existing pool filtration mechanism pumps pool water through the solar collector, and the collected heat is transferred directly to the pool.

Solar photovoltaic systems also use solar cells. There is a huge choice available, including those that are just millimetres thick and can double up as rooftop shingles and tiles, building facades or glazing for skylights.

The traditional solar cells are made from silicon, are usually flat-plate, and are very efficient. Second generation cells are called thin-film because they are manufactured from amorphous silicon or non-silicon materials, such as cadmium telluride. Third-generation technology is made from other materials, including solar inks that use conventional printing press technologies, solar dyes and conductive plastics.

Whatever system is employed, the more panels put in, the more energy will be produced, so space and aesthetics have to be taken into account, but these can be a selling point for the hotel. And most rooftop space is vast.

The Ibis Porte de Clichy hotel in Clichy, France, is one of only a few hotels to have installed a large photovoltaic system and the results are impressive. The 75-square metres of polycrystalline cells produce about 4,600kWh of electricity a year, more than it needs, which is why it also sells energy back to the national grid. “This project is unique and exemplary,” explains spokeswoman Delphine Dumonceau. “Moreover, it helps promote the brand and create an extremely positive image for the hotel.”

Jordan Valley Marriot Resort & Spa
The Jordan Valley Marriott Resort & Spa is the first hotel in the Middle East to have completed the installation of 275 solar panels to generate the energy needed to heat the property’s water.

General manager Philip Papadopoulos says: "We are proud to be the first hotel in the Middle East and most probably one of only a few worldwide to have installed such a system on this scale.

"Our aim is to have the most environmentally friendly hotels with employees that are environmentally conscious. Marriott is committed to the responsibility of protecting the environment for our employees, guests and communities."

The savings so far are as follows:

May-September 2008
Actual consumption of diesel to used heat water
51,341 litres
Actual cost
34,596 Jordan Dinars (US$ 48,796)

May-September 2009
Actual consumption of water
29,259 litres
Actual cost
9,300.098 Jordan Dinars (US$ 41,268)

Solar technology is thought of as an energy source for hot countries but cooler climates such as Canada and northern Europe can just as easily tap into the sun’s resources. In fact, Denmark is Europe’s leading country for solar energy with 44% of the total European Union output.

It’s true that the further north you go, the less solar energy you can create, but countries such as the UK still receive 60% of the solar energy of the equator. For a solar system to work, all it needs is daylight, as it can collect both direct radiation from sunlight on clear days and diffused radiation from light on cloudy days.

Continuous technology improvements make solar energy in the northern hemisphere increasingly practical and profitable. The solar thermal market in the European Union and Switzerland showed a strong growth in 2008 with an increase of over 60%.

Paradoxically, solar power can also be used very efficiently in hot climates for cooling. With up to 22% of a hotel’s total electrical expenses going on cooling systems, the potential savings are great. In fact, new techniques are being developed using solar power to run air-conditioning, ventilation systems and dehumidifiers that are just as efficient as standard systems.

Solar air-conditioning works like this. Air is passed over solid desiccants like silica gel or zeolite to draw moisture from the air to allow an efficient evaporative cooling cycle. The desiccant is then regenerated using solar thermal heat energy to dry it out in a cost-effective, continuously repeating cycle.

Solar-powered ventilation works both for heating in the winter and cooling in the summer using a low-energy fan and motor system that can be cost-effectively powered by photovoltaics, with enhanced natural convection exhaust up a solar chimney.

Dehumidifiers are created using an attractive recirculating waterfall that dehumidifies a room using solar thermal energy to regenerate the liquid and a photovoltaics-powered low-rate water pump.

And, of course, you can rig up solar photovoltaic systems to power standard electric-run cooling systems too.
Solar technology is constantly evolving as governments and manufacturers invest large sums of money in research and development.

German firm Avancis is one of the world leaders in photovoltaics and is creating ever more cost-efficient systems. Its second-generation CIS (copper, indium and selenium) system incorporates a coating of copper, indium and selenium just two thousandths of a millimetre thick that effectively absorbs sunlight. Independent tests have shown it to be 20% more efficient than older systems because, even when light levels are low, the high-energy yield technology is still very cost-effective.

Solar water heating technology is advancing all the time too. US company Cool Energy is developing a system that produces heat and electricity for the northern hemisphere. It combines a traditional solar water heater with an engine-based generator that operates at 200°C rather than the traditional 500°C.

In cool weather, it provides both hot water and heating while in warmer months, excess heat is used to drive the engine and generate electricity. It can provide 80% of the heating, 100% of the hot water and 60% of a building’s electricity needs.
Solar power has huge potential as a reliable energy source in developing countries, where traditional energy supplies can be unpredictable.

Take Botswana’s Gaborone Sun Hotel, part of the Sun International hotel group, which has the biggest solar water heating system of any hotel in Africa. Its 176 flat-plate solar panels, measuring two-by-one metres, produce 283.5MW of renewable energy. General manager Lance Rossouw explains: “Since the installation went live, it’s been a real weight off our shoulders not having to worry about coal supply. And an unexpected benefit is how efficient it is in terms of water temperature. Our average hot water temperature has increased from 45°C to 70°C.”

But there’s a long way to go for the developing world - at present, Africa, Asia and Latin America produce only 1% of the world’s total output of solar energy.

Resources and Further Reading

Abengoa Solar



Carbon Trust

Cool Energy

Eco Green Hotel

Energy Saving Trust

Energy Star

National Renewable Energy Laboratory

Renewable Energy Association

Sage Blossom Consulting

Solar Trade Association

The Met Office

Yale Environment 360

Australian & New Zealand Solar Energy Society

Canadian Solar Industries Association

European Solar Thermal Industry Federation

Florida Solar Energy Industries Association

Hotel Energy Solutions

Queensland Office of Clean Energy

Solar Energy Industries Association

Solar Trade Association

Leave a Reply